How long have you been living in the UK and not disclosing the Australian rental income? Is the UK Pounds purchase value of the property based on the 2001 exchange rate? Is the current UK Pounds value based on the current exchange rate? You say that you lived in the property for 3 years and let it for 10, yet you bought it in 2001. Can you account for the missing 2 to 3 years? In order to give you an accurate approximation of the CGT as possible, can you break down the varios stages of ownership of the property (occupied by you, let commercially, vacant but available for let and vacant and not available for let) into months please.
I have to go out but will be back in about 30 minutes.